Self propelled gun

ABSTRACT

A self propelled gun ( 2 ) comprises a vehicle ( 4 ) possessing a source of primary power ( 6 ) and a gun assembly ( 8 ) movably attached to the vehicle. The gun assembly ( 8 ) comprises a base ( 10 ), a cradle ( 14 ) pivotally mounted to the base and a barrel ( 16 ) slidably mounted to the cradle ( 14 ) such as to be displaceable from a first, run-out, position to a second, recoiled, position as a consequence of the barrel ( 16 ) recoiling on firing. The gun assembly ( 8 ) is movably mounted to the vehicle ( 4 ), preferably by a pivot arrangement ( 24, 26 ) between vehicle ( 4 ) and base ( 10 ), such that in a first, “mobility”, mode the gun assembly ( 8 ) is free of any direct contact with the ground ( 42 ), and said barrel ( 16 ) points in a first direction allowing said vehicle ( 4 ) to be driven and a second, “firing”, mode of operation in which the gun assembly is deployed to a firing position in which the base moves towards and into engagement with the ground ( 42 ). During deployment of the gun assembly ( 8 ) the barrel ( 16 ) is deployable through an angle of elevation which differs from said first direction by at least ninety degrees.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a self propelled gun.

2. Discussion of Prior Art

Mobility is a key factor in modern warfare and for any piece ofartillery to play a valuable part on the battlefield it must be ablerapidly to reach the scene of conflict, that is it must be able rapidlyto be tactically deployed. Although there is a wide range of fieldartillery such as tanks, self propelled howitzers and guns, towed fieldhowitzers and guns and self propelled mortars, each has its ownweaknesses in rapid deployment scenarios.

Tanks, for example, are heavy (50-60 Tonnes), well armoured trackedvehicles with a turret mounted medium calibre gun (105-140 mm) which aregenerally used on line of sight, short range engagements. Although asingle tank can be transported by the heaviest lift aircraft, suchaircraft are restricted by the availability of suitable landing sitesand therefore tanks can only be strategically deployed by air and haveto be transported by ship, rail or under their own power to the scene ofconflict which can be many thousands of kilometers from such a landingsite. Furthermore whilst readily mobile once on the battlefield, theyare incapable of carrying substantial amounts of ammunition.

Self propelled howitzers are heavy (30-60 Tonnes), relatively lightlyarmoured tracked vehicles with a medium calibre gun (typically 155 mm)which is often turret mounted. Generally this armament is deployed wellbehind the front line as an indirect fire weapon with barrel elevationsof between −5° and 70° and has a range of up to 40 kilometers. As withtanks transporting this type of armament by air is impractical anddeployment to a conflict must rely on ships, trains or their ownmobility.

Self propelled guns are medium weight multi-wheeled or tracked vehicleshaving a medium calibre gun mounted on the rear of the vehicle. Toassist in absorbing some of the energy when the gun is fired it is knownfor them to include one or more deployable spades at the rear of thevehicle which is/are lowered into engagement with the ground beforefiring.

Field howitzers and guns weigh up to 10 Tonnes and are an unarmouredindirect fire weapon, with a calibre up to 155 mm and a range up to 30km. They can also be employed in a direct fire mode. Although somedesigns can have an auxiliary power unit (APU) giving very limitedmobility on the battlefield they are normally towed by a lorry to, andaround, the battlefield. Whilst air transportable by a fixed wingaircraft or helicopter, they are reliant upon lorries which also have tobe transported to the battlefield for supplying them with ammunition.

A self propelled mortar is a relatively heavy (25-30 tonnes) lightlyarmoured tracked vehicle with a large calibre (240 mm) mortar. Generallythey are an indirect fire weapon which is used at high elevation angles(45° to 80°) and has a range of 10 km or 18.0 km with rocket assistance.In contrast to other types of artillery described the barrel has asmooth bore (not rifled) and is not trunnion mounted. As with tanks andself propelled howitzers this type of armament is not practical todeploy by air.

SUMMARY OF THE INVENTION

The inventors have appreciated that a need exists therefore for an airtransportable, high mobility, medium calibre self contained weapon. Thepresent invention has arisen in an endeavour to provide a such a weaponwhich, in part at least, overcomes the limitation of the known guns.

According to the present invention a self propelled gun comprises: avehicle possessing a source of primary power and a gun assembly, saidgun assembly comprising a base; a cradle pivotally mounted to the baseand a barrel slidably mounted to the cradle such as to be displaceablefrom a first to a second position as a consequence of the barrelrecoiling on firing characterised in that the gun assembly is movablymounted to the vehicle such that in a first, “mobility”, mode the gunassembly is free of any direct contact with the ground, and said barrelpoints in a first direction allowing said vehicle to be driven and asecond, “firing”, mode in which the gun assembly is deployed to a firingposition in which the base moves towards and into engagement with theground and wherein said barrel is deployable through an angle ofelevation which differs from said first direction by at least ninetydegrees.

A particular advantage of the self propelled gun of the presentinvention is that since the base is in contact with the ground duringfiring the effective height of the pivot about which the cradle andbarrel are mounted, that is the height above the ground, is minimisedwhich reduces the effect of overturning forces making the gun morestable in operation. In contrast to the known self propelled guns thevehicle of the present invention does not carry the full shock loadduring firing and this enables the use of a comparatively lighter weightvehicle having a standard suspension arrangement.

Advantageously the first direction is in a substantially horizontalforward direction such that when the gun assembly has been deployed tothe “firing” mode the barrel is directed in a direction which isvertical or substantially away from the vehicle. This provides theadditional advantages that:

(i) the vehicle acts as a virtual trail leg in that it increases themass inertia of the gun assembly and helps counter the overturningmoment of the recoil force, especially when firing at low angles ofbarrel elevation thereby eliminating the need for a deployable spade ortrail legs; and

(ii) since the barrel is directed away from the vehicle it is capable ofoperating through a large range of barrel elevations from a small angleof depression to a high angle of elevation without the vehicleobstructing the gun assembly.

Preferably the first direction is additionally substantially coincidentwith the axis of the vehicle and the barrel is swung vertically upwardsduring deployment. This allows the sides of the vehicle deck to be usedfor storage of a substantial number of shells and charges, crewaccommodation and auxiliary equipment thereby enabling the selfpropelled gun to operate as a self contained unit.

Preferably the gun assembly is movably mounted to the vehicle by thebase being pivotally attached to the vehicle by a pivot arrangement. Ina particularly preferred arrangement the pivot arrangement is configuredsuch that deployment of the base into engagement with the ground raisesa part of the vehicle in proximity with the pivot arrangement away fromthe ground. This is particularly advantageous since a proportion of thevehicle's weight bears down through the pivot arrangement onto the baseto assist in holding the gun assembly securely in contact with theground when the gun is positioned and fired.

The barrel can be of normal or extended length (long range).Advantageously the barrel is held in the second position, i.e. in afully recoiled position, during the “mobility” mode to reduce theoverall length of the self propelled gun and any overhang of the barrelbeyond the vehicle. This is particularly advantageous in that it assistsin providing unobscured driver vision and is of additional benefit whenthe gun is being transported by air where space is at a premium. Thus,in practice, after the last round has been fired, the barrel is held inthe fully recoiled position. Preferably the barrel is held in the secondposition when deploying the gun assembly from the “mobility” to “firing”mode and vice versa. This has the further advantage that the centre ofgravity of the barrel is shifted towards the trunnion bearing thusreducing the out of balance of the gun assembly during deployment and/orstowage which reduces the duty on the means for deploying the gunassembly. This is especially so when deploying the gun assembly with thevehicle on, and disposed transversely to, an inclined surface.

In a particularly preferred embodiment the cradle is pivotally mountedabout a bearing which is positioned beyond the maximum point of recoilof the barrel thereby minimising the bearing height whilst stillenabling the barrel to be elevated to high angles of elevation.

Advantageously the base incorporates one or more spades, whichconveniently comprises one or more rearwardly angled blades on theunderside of the body, which is/are such as to dig into the groundduring recoil thereby enhancing the transmission of the recoil forces tothe ground.

BRIEF DESCRIPTION OF THE DRAWING

For a clearer understanding of the invention a self propelled gun inaccordance with the invention will now be described, by way of exampleonly, with reference to the accompanying drawings in which:

FIG. 1 is a schematic side elevation of a self propelled gun inaccordance with the invention in a “mobility” mode;

FIG. 2 is a front elevation of the self propelled gun of FIG. 1;

FIG. 3 is a side elevation of the self propelled gun of FIG. 1 in a“firing” mode;

FIG. 4 is a schematic representation of the connection between the gunassembly and the vehicle in the “mobility” mode;

FIG. 5 is a schematic representation of the connection of FIG. 4 between“mobility” and “firing” modes;

FIG. 6 is a schematic representation of the connection of FIG. 4 in the“firing” mode; and

FIG. 7 is a schematic representation of the self propelled gun of theinvention in the hold of an aircraft.

DETAILED DESCRIPTION OF THE DRAWING

Referring to FIGS. 1 to 6 there is shown a self propelled (SP) gun orhowitzer 2 in accordance with the invention in a “mobility” mode, thatis a mode for travelling to and from a point of firing. The SP gun 2comprises a multi-wheeled vehicle 4 having a primary source of power 6and a gun assembly 8 movably mounted to the rear of the vehicle 4. Thevehicle 4 preferably comprises an all wheel drive vehicle such as a10×10. It will be appreciated however that other chassis configurationsor tracked vehicles can also be used.

The gun assembly 8 comprises a base 10, a saddle (or trunnion supportstructure) 12, a cradle 14 and a barrel 16. The barrel 16, whichpreferably comprises a 52 calibre 155 mm rifled bore barrel, is slidablymounted to the cradle 14 such as to be displaceable from a first, runout or firing, position to a second, recoiled, position as a consequenceof the barrel 16 recoiling on firing. A hydro-pneumatic recoil bufferand recuperator system (not shown) is provided to absorb some of theenergy when the barrel 16 recoils during firing. It will be appreciatedthat other types of energy absorbing systems can be utilised such as forexample hydraulic, mechanical spring, electro-magnetic brake orelectro-rheological devices.

In a particularly preferred implementation the cradle 14 is constructedfrom hollow members preferably in the form of four lightweight tubes 14a-14 d (as shown in FIG. 2) and the volume within the tubes is utilisedto store the compressed gas for the hydro-pneumatic recuperator/bufferas is described in our UK patent GB 2313180, the content of which ishereby incorporated by way of reference thereto. A particular advantageof utilising the hollow cradle members to store the compressed gas isthat this eliminates the need to use separate gas storage accumulatorswhich reduces the weight of the gun assembly 8.

The cradle 14 has a pair of journals projecting coaxially from oppositesides which are pivotally mounted in a respective trunnion bearing 18 inthe saddle 12 such that the barrel 16 can be elevated from low angles ofdepression e.g. −5° to high angles of elevation e.g. +70°. The barrel 16is preferably slidably mounted within the cradle 14 such that the axisof the trunnion bearing is located substantially at, or beyond, themaximum point of recoil of the barrel 16 as described in our UK patentGB 2313178, the content of which is hereby incorporated by way ofreference thereto. That is the barrel 16 is mounted in a forwardposition within the cradle 14 such that the breech 16A of the barreldoes not pass through the axis of the trunnion bearing as a consequenceof recoil on firing of the gun assembly 8. This is best illustrated inFIG. 4 which shows the barrel secured in a fully recoiled position. Thisis particularly advantageous in that it allows the height of thetrunnion bearing 18 to be minimised whilst still allowing the barrel 16to be elevated to high angles of elevation and thereby reduces theoverturning moments on the saddle 12 during firing. Since the barreldoes not recoil through the axis of the trunnion bearing, the cradle canbe pivotally mounted to the saddle 12 by a solid axle rather than atrunnion mounting in alternative embodiments.

A pair of hydraulic elevating servo-actuators 20 are provided onopposite sides of the cradle 14 to elevate the barrel 16 to a desiredelevation. Each hydraulic elevating actuator 20 comprises a piston 20Aand cylinder 20B in which the piston 20A is pivotally attached to thecradle 14 and the cylinder 20B is pivotally attached to a respectivepart 22 of the saddle 12. Hydraulic power to operate the elevatingactuators 20 is derived from the vehicle's primary power source 6, whichcan be supplemented using scavenged energy from the buffer/recuperatorsystem. Activation of the hydraulic elevating actuators 20 causes theirlength to extend or contract thereby elevating the barrel 16. Whilst itis preferred to use hydraulic elevating servo-actuators other forms ofactuators can be used such as electric rotary or linear servo motors.

The saddle 12 is pivotally mounted to the base 10 by a training bearing(not shown) to allow training of the gun assembly 8 over an arc ofapproximately ±30°. Extending from and fast with the base 10 are a pairof connecting members 24 for pivotally attaching the gun assembly 8 tothe rear of the vehicle 4 about a bearing 26. The bearing 26 is locatedclose to the vehicle's transmission height. The gun assembly 8 ismovable about the bearing 26 by means of a hydraulic actuator 28 whichcomprises a piston 28A and cylinder 28B arrangement. The piston 28A ispivotally attached to a respective lever member 30 which is fast withthe member 24 and the cylinder 28B is pivotally attached to the vehicle4. The lever member 30 and connecting members 24 are configured suchthat an extension or contraction in the length of the actuator 28 causesthe base 10 to pivot about the bearing 26.

Primary power is provided from pack 6 to drive the vehicle 4 as well asto deploy and operate the gun assembly 8. The vehicle 4 has cabs 32 and34 for the crew which are isolated from respective shell 36 and charge38 magazines which are located along the side of the vehicle deck. Themagazines 36, 38 are divided into active (automatic loading) 36A, 36Band passive fixed containers 36B and 38B. Each active magazine 36A, 36Bis respectively capable of typically holding forty-five shells andcharges whilst the two passive magazines can each hold a further fifteenrounds. It will be appreciated that the total amount of ammunition(shells and charges) and the ratio of the active passive storage can betailored to suit a given application. As illustrated the magazines 36,38 lie within the vehicle chassis walls along the length of the vehicleand are separated by a central access corridor 50. The sidewalls of thecharge magazine 38 provide physical isolation of the shells and charges.An automatic ammunition handling system (not shown) is provided forautomatically loading the charges and shells at a typical minimum rateof eight rounds per minute. The ammunition handling system preferablycomprises a walking-beam arrangement for each active magazine for movingthe shells and charges within the magazines to the rear of the vehicle 4and one or more mechanical arms for transferring them onto a loadingtray for automatic ramming. The SP gun 2 of the present invention isthus a totally self contained unit.

FIG. 3 shows the SP gun 2 in a “firing” mode in which the gun assembly 8is deployed and the base 10 engages the ground 42. A spade 44 which isdetachably fastened to the underside of the base 10 is shown dug intothe ground 42. The spade 44 is preferably in the form of one or morerearwardly angled chevron blades which is/are designed to dig into theground 42 and to transmit the forces during firing. In the “firing” modea part of the vehicle 4 adjacent to the gun assembly 8 is lifted suchthat a part of the weight of vehicle 4 bears down through the bearing 26onto the base 10 to assist in holding the gun assembly 8 securely incontact with the ground 42. At the angle of elevation shown in FIG. 3and high elevation angles, i.e. +30° to +70°, the majority of the recoilforce is directed vertically and is transmitted into the ground 42 viathe base 10. At low angles of elevation and at angles of depression i.e.+30° to −5°, the majority of the recoiling force induces an overturningmoment about the spade which is absorbed wholly or in part by the massof the vehicle 4 which thus acts as a virtual trail leg. The location ofthe trunnion bearing 18 beyond the limit of maximum recoil, gives thegun assembly 8 a high degree of positive out-of-balance and this is ofmost benefit at low angles of elevation where the out-of-balance turningmoment will act to drive the spade 44 into the ground. The result isthat, when fired, the angled blade 44 acts as a static plough to absorba substantial part of the recoil forces such that only a minority istransferred to the vehicle 4.

FIGS. 4, 5 and 6 show the principle of the deployment of the gunassembly 8 between the “mobility” and “firing” modes. Referring to FIG.4, this shows the gun assembly 8 in the “mobility” mode in which the gunassembly 8 is free of any direct contact with the ground 42 and thebarrel 16 is stowed in a substantially horizontal forward pointingdirection. In the “mobility” mode the base 10 is pivoted into asubstantially vertical orientation. A door 46 is provided on the end ofthe corridor 50 between the shell and charge magazines 36, 38.

To deploy the gun assembly 8 the hydraulic actuator 24 is activated suchthat the base 10 pivots about the bearing 26 from a substantiallyvertical orientation to a substantially horizontal orientation, at whichpoint it is in engagement with the ground 42 as shown in FIG. 5. Theposition of the bearing 26 above the ground and the connecting member 24are configured such that deployment of the gun assembly 8 drives thespade 44 into the ground 42 and raises the rear of the vehicle 4 awayfrom the ground 42. At this point of the deployment the barrel 16 is ina substantially vertical elevation. The hydraulic actuator 20 is thenactivated to deploy the barrel 16 to a desired firing elevation as shownin FIG. 6.

In the “firing” mode the barrel 16 is directed either substantiallyvertically or away from the vehicle 4. During deployment of the gunassembly 8 the barrel 16 traverses an angle of at least 90° such that itis directed away from the vehicle 4. This enables the gun assembly 8 tobe operated with depressed angles of elevation of the barrel 16 withoutthe vehicle obstructing the gun assembly 8. It will be appreciated thatin the “firing” mode the SP gun 2 effectively has a three point support,i.e. the base 10 and the sets of wheels near the front of the vehicle 4.

To deploy the gun assembly 8 from the “firing” to the “mobility” modethe reverse of the above procedure is used i.e. the barrel 16 iselevated to a substantially vertical elevation by activation of theactuator 20 and the whole gun assembly 8 is pivotally lifted clear ofthe ground 42 and into a stowed position within the vehicle 4 byactivating actuator 24. To reduce the turning moment required by theactuators 20 and 24 the gun assembly 8 is preferably stowed with thebarrel 16 in a fully recoiled position such that the centre of gravityof the barrel 16 is moved toward the trunnion bearing 18. Stowing thebarrel 16 in this way is also advantageous as it reduces the overalllength of the SP gun 2 and any overhang of the barrel beyond thevehicle, which assists in providing un-obscured driver vision and is ofbenefit when the gun is to be transported by air. Preferably the barrel16 is clamped in place when in the “mobility” mode.

Whilst it is preferred to operate the hydraulic actuators 20, 24 in theorder described this is not essential. In an alternative arrangement theactuators 20 and 24 can be operated simultaneously which would reducethe time taken to deploy the gun assembly 8 between the “mobility” and“firing” modes. However deploying the gun assembly 8 in two stagesprovide the following advantages. By firstly moving gun assembly 8 intoa vertical position (FIG. 5), the centre of gravity of the elevatingmass is effectively moved closer to the trunnion bearing 18, rather thanto the right of it as shown in FIG. 3. This considerably reduces theturning moment needed to be generated by the hydraulic actuator 24.Secondly, after firing a few rounds the spade 44 will be embedded in theground 42 and, in muddy conditions, the blade 46 and the underside 10Aof base 10 may be held by a suction force. A larger turning moment willtherefore need to be generated by the actuator 24 to break the suctionbetween base 10/spade 44 and the ground 42. It is quite possible thatthe suction force could be of a significant magnitude compared to theweight of the gun assembly 8. Thus, it is preferred that the barrel 16is moved to the vertical position (FIG. 5) before operating thehydraulic actuator 24. In order to assist the lifting effort of theactuators 24 the vehicle 4 can be driven slightly forwards and/orbackwards to help to break the suction.

It will be appreciated that the actuator 24 has to be designed for avery considerable duty, including a necessary margin of reserve to coverthe exigencies which might occur on a battlefield, e.g. emergencyoperation of the actuator 24 before operating the actuators 20 havefully completed their motion to bring the cradle 14 and barrel 16 to thevertical for rapid escape.

The SP gun 2 of the present invention is designed to be airtransportable and therefore minimising weight is a prime consideration.Since the recoil of a 155 mm gun is a violent process it is advantageousto utilise every means to dissipate these forces. In a particularlypreferred implementation a pressure relief valve is incorporated intothe hydraulic elevating actuators 20 to allow limited rotationalmovement of the base 10 about the bearing 26 during firing. Convenientlythis valve is in the form of a hydraulic switch which is operable toopen when subjected to high impulses of force as would be experiencedduring firing and to close at normal operating forces. This limitedfreedom of movement allows the spade 44 to dig in more deeply andprotect the actuator 20 and mounting members from damage. The hydraulicactuators 20 thus provide an element of selective damping to cushion theworst of the recoil forces. As the effect of the recoil and reboundends, automatic hydraulic systems re-energise the actuators 20 tore-establish the firing attitude, i.e. urge the base 10 firmly intoengagement with ground 42 and raise the rear of the vehicle 4.

As shown in FIGS. 1 and 3 the shell and charge magazines 36, 38 arelocated near the rear of the vehicle 4 such that their weightadditionally urges the base 10 downward into engagement with the ground42 thereby assisting in stabilising the gun assembly 8 during firing.Furthermore, since shells and charges 36, 38 are automatically movedtowards the rear of the vehicle 4 each time a round is fired, thisensures that the maximum possible amount of weight acts to stabilise thegun assembly 8. This being said it will be appreciated that the SP gunof the present invention is designed for stable operation even withoutammunition on board and that the effect therefore of the ammunitionfurther assists in stabilising the gun assembly.

In the “mobility” mode, as shown in FIGS. 1 and 2, the barrel 16 restson the roof of the corridor 50.

In operation of the SP gun 2 a target's position would be given and theco-ordinates of the firing position fed into an onboard gunnery computerwhich calculates the range and bearing of the target. Using an on-boardnavigation system the vehicle 4 is driven to the firing position and isoriented in a direction facing directly away from the target. The gunassembly 8 is deployed into the “firing” mode, such that it is pointingtowards the target, and a number of rounds can be fired in rapidsuccession at different trajectories such that the rounds arrive at thetarget at substantially the same time. The gun assembly 8 is immediatelyswung back into the “mobility” mode and the vehicle moved to anotherlocation to reduce any likelihood of retaliation.

The powered deployment system described allows the gun assembly 8 tostart being deployed automatically the instant the vehicle 4 stops. Italso allows the vehicle 4 to be driven away as soon as barrel 16 comesdown onto the roof of the corridor 50. This gives the SP gun 2 of theinvention a level of mobility similar to that of a tank or a selfpropelled howitzer. However its weight, typically less than twentytonnes when fully loaded, is substantially less than a tank making itpossible to tactically deploy it by air using, for example, a short takeoff and landing aircraft such as a Hercules C-130 as illustrated in FIG.7. Furthermore, due to its high mobility there is no need for heavyprotective armour other than lightweight Appliqué armour along the sidesof the vehicle. This is a further source of weight saving.

Since the barrel 16 is located along the axis of the vehicle in the“mobility” mode and is raised vertically when being deployed into the“firing” mode this enables the sides of the vehicle to be used forcarrying ammunition.

It will be appreciated by those skilled in the art that the presentinvention is not limited to the specific embodiment described and thatmodifications can be made which are within the scope of the invention.

What is claimed is:
 1. A self propelled gun comprising: a vehiclepossessing a source of primary power and a gun assembly, said gunassembly comprising: a base; a cradle pivotally mounted to the baseabout a bearing; and a barrel slidably mounted to the cradle such as tobe displaceable from a first to a second position as a consequence ofthe barrel recoiling on firing, wherein the gun assembly is movablymounted to the vehicle such that in a first, “mobility”, mode the gunassembly is free of any direct contact with the ground, and said barrelpoints in a first direction allowing said vehicle to be driven and asecond, “firing”, mode of operation in which the gun assembly isdeployed to a firing position in which the base moves towards and intoengagement with the ground and wherein said barrel is deployable throughan angle of elevation which differs from said first direction by atleast ninety degrees, said bearing is positioned at a point beyond themaximum recoil of the barrel.
 2. A self propelled gun according to claim1 in which the first direction is in a substantially horizontal forwarddirection.
 3. A self propelled gun according to claim 1 in which thefirst direction is substantially coincident with a longitudinal axis ofthe vehicle.
 4. A self propelled gun according to claim 1 in which thegun assembly is movably mounted to the vehicle by the base beingpivotally attached to the vehicle by a pivot arrangement.
 5. A selfpropelled gun according to claim 4 in which the pivot arrangement isconfigured such that deployment of the base into engagement with theground raises a part of the vehicle in proximity with the pivotarrangement away from the ground.
 6. A self propelled gun according toclaim 1 in which the barrel is held in the second position during the“mobility” mode.
 7. A self propelled gun according to claim 1 in whichthe barrel is held in the second position during deployment of the gunassembly from the “mobility” to “firing” mode and vice versa.
 8. A selfpropelled gun according to claim 1 in which the cradle (14) is pivotallymounted about a bearing (18) which is positioned at a point beyond themaximum recoil of the barrel.
 9. A self propelled gun according to claim1 in which the base incorporates one or more spades.